a. Field of Invention
This invention relates to production of high grade cokes for use in graphite electrodes, etc.. More particularly, it is concerned with a simple, but very effective method for obtaining cokes from hydrocarbon compounds having large molecular weight or mixture of hydrocarbon compounds containing such large molecular weight hydrocarbons such as crude petroleum oil, distilled residue oils, ethylene cracker bottom oil, various pyrolytic tars and pitches, coal tar, coal pitch, and so on.
B. Discussion of Prior Art
Heretofore, many a method has been proposed as to production of cokes, among which "delayed coking method," "fluid coking method," and "oven method" are still existing and operating on an industrialized scale. However, in these existing coking methods, there are various problems still to be solved to eliminate disadvantages inherent thereto.
For example, in the delayed coking method, raw material oil is heated to a coking temperature through a tubular heating furnace, after which it is sent into a coking drum. An important problem in this case is how to prevent the tubular heating furnace from being clogged due to the coking. Various efforts have been exerted to solve this problem by stringent control of the heating temperature, pressure, and flow rate of the raw material through the tubular furnace, etc., or, in many cases by adding steam or other fluid medium to the raw material within the tubular heating furnace. However, these operations are not only not directed to improvement in quality of the produced cokes, but also result in sacrificing the optimum treating conditions for the grade of cokes. With increased demand for HP or UHP electrodes for metallurgy and so forth in recent years, production of high grade, needle-shaped cokes has been desired more and more. On the other hand, from the aspect of the raw material for cokes, there has been a tendency such that a larger quantity of various pyrolytic tars and oils is being produced as by-product in petrochemical industries. Although these materials are generally suitable as the raw material for needle-shaped cokes in view of their composition and molecular structure, they tend to be thermally unstable, which brings about various difficulties in the heating operation with the delayed coking method, in which the tubular heating furnace is used.
Also, in the oven method where the raw material oil is heated through a partition wall, it may be possible to control the relationship between the heating temperature and time. In this case, however, as the heat transfer speed is remarkably low, the structure of the furnace, reaction temperature, and other conditions are considerably restricted. Furthermore, the raw material oil in the oven cannot be maintained at a uniform temperature throughout, because agitating power, due to convection of heat, as well as gas spontaneously generated within the furnace, is too slight to produce the required agitation. Moreover, there is no way of expelling heat from the furnace, wherein an exothermic reaction raises the temperature of the furnace interior. After all, it is not easy to obtain homogeneous, high grade cokes even by this method.